Various patents of prior art teach filler caps utilizing mechanical springs for the generation of pressure to maintain the respective filler caps in the closed position, and in the closed and open position, selectively. These teachings include, but may not be limited to, the following examples and references:
______________________________________ Harris 1,277,918 Sept. 3, 1918 220-35 Kehoe 1,410,102 March 21, 1922 220-35 Heusser 1,720,789 July 16, 1929 220-35 Getz et al. 2,751,109 June 19, 1956 220-35 Thompson 2,769,566 Nov. 6, 1956 220-44 Kohler 848,965 Sept. 11, 1952 220-35 (Germany, 1 sheet drawing, 3 pages spec.) ______________________________________
The mechanical springs, primarily of the helical expansion and compression types, selectively, employed in that prior art display several disadvantages. They require at least one stationary pivot configuration, which occupies considerable space exteriorly with respect to the filler neck, or a corresponding structural support inside the filler neck, thereby obstructing access to the filler neck and to the vessel on which the filler neck is mounted. The springs used in these teachings become fully compressed and exert the largest pressure when not required for maintaining the closed or the open filler cap position, but apply only a fraction of the available pressure when the filler cap is in the closed or in the open position. This results in the third objectionable factor, namely, the low resistance to shock, vibration and unscheduled filler cap openings or closings upon inadvertent contact with the open or closed filler cap.